''Eustenopus villosus'' is a species of

true weevil True most commonly refers to truth, the state of being in congruence with fact or reality. True may also refer to: Places * True, West Virginia, an unincorporated community in the United States * True, Wisconsin, a town in the United States * Tr ...

known as the yellow starthistle hairy weevil. It is used as an agent of

biological pest control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...

against the

noxious weed A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is injurious to agricultural or horticultural crops, natural habitats or ecosystems, or humans or liv ...

yellow starthistle ''Centaurea solstitialis'', the yellow star-thistle, is a species of thorny plant in the genus ''Centaurea'', which is part of the family Asteraceae. A winter annual, it is native to the Mediterranean Basin region and invasive in many other ...

(''Centaurea solstitialis''). The adult weevil is hairy and brown with white stripes. It is 4 to 6 millimeters long, not including its long snout. The female chews a hole in a closed flower head, deposits an egg inside, and seals the hole with a dark-colored mucilage. This visible hole can warp the shape of the flower head as it grows. The

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

emerges from its egg in about three days and begins to feed on the flower parts and developing seeds. In just over two weeks the larva can destroy all or nearly all of the developing seeds. It uses the scraps to build a chamber in which it

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

tes for one to two weeks and then leaves the flower head as an adult. Both larva and adult of this species contribute to the damage done to the plant. The larvae eat the seeds in mature flower buds and the adults feed on smaller buds, destroying many. This weevil will readily attack many invasive ''Centaurea'' species, but has not been known to damage native flora. This weevil is native to southern Europe and the Mediterranean. It was first released as a biocontrol agent in the United States in 1990 and it is now established in much of the western United States wherever yellow starthistle grows. It is considered one of the more efficient yellow starthistle biocontrol agents.

References

* Coombs, E. M., et al., Eds. (2004). ''Biological Control of Invasive Plants in the United States''. Corvallis: Oregon State University Press, 427.

External links

USACE Biocontrol Profile
Lixinae Insects used for control of invasive plants Biological pest control beetles {{Curculionidae-stub